1. Field of the Invention
The present invention relates to an optical device and a projector.
2. Description of Related Art
Conventionally, a projector provided with a plurality of light modulation devices that modulate a light beam emitted from a light source in accordance with image information to form an optical image, a color synthesis optical device that synthesizes and emits the light beam that has been modulated in each light modulation device, and a projection optical device that projects the light beam that has been synthesized in the color synthesis optical device in an enlarged manner has been known.
As the light modulation device, e.g., an optical modulator of an active matrix drive type in which an electro-optic material such as a liquid crystal is encapsulated between a pair of substrates is adopted in general. More specifically, the pair of substrates that constitute the optical modulator includes a drive substrate and an opposed substrate. The drive substrate is arranged on the light beam emission side and has a data line, a scanning line, a switching device, a picture electrode and the like for applying a drive voltage to the liquid crystal formed thereon. The opposed substrate is arranged on the light beam incident side and has a common electrode, a black mask and the like formed thereon.
Further, a light incident side polarization plate and light emission side polarization plate that allow a light beam having a predetermined polarization axis to transmit therethrough are arranged on the light beam incident side and light beam emission side, respectively.
When the light beam emitted from the light source irradiates the optical modulator, the light is absorbed by a liquid crystal layer as well as by the data line and scanning line formed on the drive substrate or the black mask formed on the opposed substrate, so that the temperature of the optical modulator tends to be increased. Further, of the light beams emitted from the light source and transmitted through the optical modulator, the light beam that does not have a predetermined polarization axis is absorbed by the light incident side polarization plate and light emission side polarization plate, so that heat tends to be generated in the polarization plates.
To cope with the above problem, as the projector incorporating such an optical element, a configuration that includes a cooling device using a cooling fluid in order to alleviate the temperature rise in the optical element has been proposed (refer, for example, to Reference 1: Japanese Patent Laid-Open Publication No. Hei 3-174134).
More specifically, the cooling device disclosed in the Reference 1 is constituted by a casing having substantially a rectangular solid shape whose opposed end faces are opened, and the casing includes a fluid-filled cooling chamber inside thereof. An optical modulator is arranged on one end face side and a light incident side polarization plate is arranged on the other end face side. The optical modulator and light incident side polarization plate close the opened opposed end faces to form the cooling chamber. This configuration releases the heat, which has been generated in the optical modulator and light incident side polarization plate by a light beam emitted from a light source, directly into the cooling fluid.
However, in the cooling device disclosed in the Reference 1, a cooling fluid is encapsulated in the cooling chamber, so that the cooling fluid tends to be warmed by the heated optical modulator and polarization plate, allowing the warmed cooling fluid to stay in the cooling chamber. Accordingly, the temperature difference between the optical modulator and cooling fluid becomes smaller, making it difficult to effectively cool the optical modulator.
To solve the above problem, a configuration in which the cooling fluid is constantly circulated such that the cooling fluid in the cooling chamber is once guided outside the chamber and again introduced into the cooling chamber can be considerable. As the above configuration, a liquid cooling system disclosed in, for example, Reference 2 (Japanese Patent Laid-Open Publication No. 2003-233441) can be taken as an example.
In the liquid cooling system disclosed in the Reference 2, a pump, a jacket and a reserve tank are mounted on a radiator plate. The pump, jacket, and reserve tank are connected to each other through a tube or pipe so as to circulate the cooling fluid. By incorporating the liquid cooling system in the projector disclosed in the Pat. Reference 1, that is, by replacing the jacket constituting the liquid cooling system with the above cooling device, the cooling fluid is forcibly drawn out and introduced by the pump. As a result, the cooling fluid in the cooling chamber is constantly circulated to prevent the warmed cooling fluid from staying in the cooling chamber, thereby effectively cooling the optical modulator.
However, in the configuration as the above liquid cooling system in which the cooling fluid is circulated, the volume of the cooling fluid in the liquid cooling system tends to be reduced due to moisture transmission from the components in the circulation path. Here, a configuration in which extra cooling fluid is previously accumulated in the reserve tank in consideration of the decrease of the cooling fluid. It is necessary to request the manufacturer of the product to perform the replenishment of the cooling fluid in the case where the volume of the cooling fluid has fallen outside the guaranteed operating range after use during a predetermined period, imposing extra burden on the user or manufacturer. Further, when the user of the product himself or herself replenishes the liquid cooling system with a new cooling fluid, there is a possibility that the cooling fluid leaks into the inside of the product.